The operation of idle mode is described in IEEE 802.16e. Either a mobile station (MS) or a base station (BS) could initiate the idle mode operation using DREG-REQ and DREG-CMD messages, respectively. After an MS has entered the idle mode, the MS uses fixed parameters for the paging cycle, paging offset, paging listening interval and paging unavailable interval. If an MS is paged, the MS re-enters the radio access network using code based ranging and RNG-REQ/RSP messages. An MS should perform a location update upon entering a new paging area.
One concern with IEEE 802.16e idle mode design is that the exact location of the paging message(s) is not pre-determined. Therefore, an MS has to remain awake during the entire paging listening interval (PLI) searching for paging message(s) (i.e., MOB_PAG-ADV( ) messages) that may include the paging group identity(s) (PGID) assigned to the MS before the MS entered idle mode.
There are several attempts to enhance the idle mode design in IEEE 802.16e.
One attempt uses a quick paging indicator. In this design, an MS first checks whether this paging indicator is positive or not. If the paging indicator is negative, the MS would not listen any further and could return to a paging unavailable interval immediately. If the paging indicator is positive, the MS would stay awake and search for paging message(s) to see if the MS is paged or not. A concern with this design is the fineness of the quick paging indicator. In other words, the quick paging indicator may not be of much help because the paging indicator would be positive most of the time if there are many MSs in idle mode because the indicator would be positive if any of those MSs needed to be paged.
Another attempt segments the paging message into several smaller messages since the MOB_PAG-ADV( ) may be of a large size if only one message is sent to all MSs in a paging cycle. In this design, each message would carry a last paging indicator (LPI) so that an MS could stop the PLI immediately if the LPI indicates there is no more paging message in this paging cycle. A yet another attempt uses a paging location indicator so that an MS does not have to search for the paging message during the entire PLI. However, both of these attempts require explicit signaling in order for the MS to know where the LPI or paging location indicator is located in the paging cycle.
Accordingly, there is a need in the art for a system and method for effectively handling idle mode in an advanced wireless system. In particular, there is a need for a system and method for handling idle mode that effectively reduce power consumption as required, for example, by IEEE 802.16m.